The present application is based on and claims priority to Japanese Patent Application No. 11-170731, which was filed on Jun. 17, 1999, the entire contents of which are hereby expressly incorporated by reference. The entire contents of Japanese Patent Application No. 11-75968, which was filed on Mar. 19, 1999, are also hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to an air induction system of an internal combustion engine. More particularly, the present invention relates to an induction system of a small watercraft engine that powers a water propulsion device.
2. Description of Related Art
As personal watercraft have become popular, they have become increasingly fast. Today, personal watercraft are capable of speeds greater than 60 mph. To attain such speeds, personal watercrafts are driven by high power output motors.
Typically, two-cycle engines are used in personal watercraft because two-cycle engines have a fairly high power to weight ratio. One disadvantage of two-cycle engines, however, is that they produce relatively high emissions. In particular, large amounts of carbon monoxide and hydrocarbons are produced during operation of the engine. When steps are taken to reduce these emissions, other undesirable consequences typically result, such as an increase in the weight of the engine, the cost of manufacture, and/or the reduction of power.
It has been suggested that four-cycle engines replace two-cycle engines in personal watercraft. Four-cycle engines typically produce less hydrocarbon emissions than two-cycle engines while still producing a relatively high power output. However, adapting four-cycle engines for use in personal watercraft has its own engineering and technical challenges.
For example, four-cycle engines include certain components not found in two-cycle engines. Some of these components are particularly susceptible to corrosion by water, especially salt water. Accordingly, four cycle engines often have a structure or system that prevents minimizes the invasion of water through the intake system and into the engine.
An example of such a system is disclosed in Japanese Patent Application No. 8-49596, which discloses a small watercraft having a carburetor located in a relatively high position within the engine compartment. An induction system is situated on one side of the engine and an exhaust system is situated on the other side of the engine. The induction system includes an intake pipe extending from a cylinder head and connected to the carburetor. An intake silencer is connected to an upstream side of the carburetor. The intake silencer has an air inlet formed through its bottom for drawing air from the surrounding engine compartment.
The relatively high positioning of the carburetor makes it difficult for water splashing around the engine compartment to work its way upward through the induction system and carburetor and into the engine. However, this arrangement results in a relatively high center of gravity of the engine. A high center of gravity impairs the watercraft""s ability to make swift and quick maneuvers, and also lessens the overall stability of the watercraft.
Accordingly, there is a need in the art for a small watercraft having an induction system that minimizes the invasion of water into the engine through the induction system and which maintains a relatively low center of gravity.
In accordance with one aspect, the present invention comprises a small watercraft having a hull and an engine compartment. An internal combustion engine is supported within the engine compartment. The engine comprises an engine body having an upper surface and a plurality of combustion chambers. A propulsion device is supported by the hull and driven by the engine. An induction system conducts air from the engine compartment to each of the combustion chambers. The induction system comprises an intake silencer and an intake chamber, which communicate with each other through a connection pipe. The intake silencer has an inlet which communicates with the engine compartment. The intake chamber communicates with the combustion chambers through a corresponding plurality of intake pipes. The intake pipes extend generally upwardly from the intake chamber so that the intake chamber is positioned generally lower than the upper surface of the engine body.
In accordance with a further aspect, the intake chamber of the present invention has a bottom surface which has a collection portion. The bottom surface is adapted to direct fluid to the collection portion. A drain port is positioned in the collection portion, so that fluid from the intake chamber may be evacuated through the drain port.
In accordance with another aspect of the present invention, a small watercraft has a hull and an engine compartment. An internal combustion engine is supported within the engine compartment and comprises an engine body and a crankcase. A plurality of combustion chambers are defined within the engine body. An output shaft is disposed within the crankcase and is arranged generally parallel to a longitudinal axis of the hull. A propulsion device is supported by the hull and driven by the engine. An induction system conducts air from the engine compartment to each of the combustion chambers. The induction system includes an intake silencer having an upstream chamber, a downstream chamber, and a passageway communicating with the upstream and downstream chambers. The upstream chamber has an inlet communicating with the engine compartment. The downstream chamber has an outlet.
In accordance with yet another aspect, the upstream and downstream chambers are disposed side-by-side and are separated by a dividing wall. A tortuous flow path is defined through the intake silencer between the inlet and the outlet. In accordance with a further aspect, each of the upstream and downstream chambers has a drain port.
In accordance with a still further aspect of the present invention, a small watercraft comprises a hull having a longitudinal axis and an engine compartment. An internal combustion engine is supported within the engine compartment and comprises an engine body and a crankcase. A plurality of combustion chambers are defined within the engine body. An output shaft is disposed within the crankcase and is arranged generally parallel to the longitudinal axis of the hull. A propulsion device is supported by the hull and driven by the engine. An induction system conducts air from the engine compartment to each of the combustion chambers. The induction system includes a plurality of intake pipes and an intake chamber. Each intake pipe communicates with a corresponding combustion chamber and extends generally upwardly from the intake chamber. Each of the intake pipes has an inlet within the intake chamber. The intake chamber has a top surface and a bottom surface, and the inlets are spaced from the top surface.